When planning a radiotherapy treatment for a specific patient, the distribution of the radiation dose in tissue of the patient's body is generally determined before the treatment starts. In general, a graphical display of a dose distribution is displayed within medical image information about the anatomical region of interest. The region of interest comprises a target region and off-target regions such as healthy tissue and critical structures. The information about the dose distribution is normally displayed by using a scheme of isodose lines located at predetermined (i.e. fixed) dose intervals. This may lead to problems in visually differentiating between different isodose lines in case they are situated so close to one another in a specific display mode that an operator's eye or mind cannot discern between different lines or that the operator regards the presentation as leading to discomfort when viewing it.